This invention relates to an air clutch which positively operates even with high speed rotation.
An air clutch is known in the art in which, as shown in FIG. 1, an air bellows 10 is inflated with compressed air so that a plurality of friction shoe blocks 1 abutted against the bellows 10 are caused to be brought into contact with a drum 7, thereby causing the rim 9 and drum 7 to rotate together transmitting power. With this conventional air clutch, as the number of revolutions is increased, the centrifugal force exerted on the friction shoe block 1 is increased in proportion to the square of the number of revolutions. FIG. 5 illustrates the relationships between the number of revolutions and loss of contact pressure due to centrifugal force. Therefore, it is necessary to increase the air pressure in the bellows 10 to avoid friction loss. However, there is a limiting rotational speed above which the application of the clutch of this type becomes impractical.